Wheel suspension for motor vehicles

ABSTRACT

The invention relates to a wheel suspension for motor vehicles, with at least one upper transverse arm and two lower separated transverse arms per wheel, which are each arranged at a defined angle to one another and are articulated to the body of the vehicle and also to a wheel carrier, furthermore with a track rod which acts on the steering lever of the wheel carrier and with a McPherson strut unit which, aligned at a defined angle to the vertical, is coupled to the body of the vehicle and to the forward lower transverse arm via a rubber-metal sleeve bearing. To achieve improved driving comfort of the motor vehicle it is suggested that at least the forward lower transverse arm ( 12 ) is arranged such that the coupling point ( 12   c ) of the McPherson strut unit ( 20 ) on the transverse arm ( 12 ) when the wheel is deflected viewed in the transverse direction of the vehicle ( 30 ) runs parallel to the longitudinal axis ( 28 ) of the McPherson strut unit ( 20 ).

The invention relates to a wheel suspension for motor vehicles according to the preamble of claim 1.

A wheel suspension such as this is shown, for example, in DE 38 43 613 A1 in which the lower and optionally the upper transverse arm of the wheel guidance are individual transverse arms which, in conjunction with a track rod which is articulated to the body or to the steering of the motor vehicle, form track-stable wheel guidance. The advantage of such a wheel suspension with detached transverse arms lies especially in formation of a virtual steering axle which, for the most part, can be designed independently of structural constraints so that favorable axle values such as camber, axle pin rake, roll radius, and the disturbing-force lever arm for the driven wheels (dimension a), etc. are adjustable. In conjunction with the spring system and damping of the motor vehicle there can be a McPherson strut unit with a telescoping shock absorber which is coupled in a structurally favorable manner to the forward lower transverse arm of the wheel suspension by way of a rubber-metal sleeve bearing.

The object of the invention is to propose a wheel suspension of the generic type which is further improved with respect to driving comfort.

This object is achieved according to the invention with the characterizing features of claim 1. Advantageous developments of the invention are described by the dependent claims.

According to the invention, it is proposed that at least the front lower transverse arm is arranged such that the coupling point of the McPherson strut unit on the transverse arm when the wheel is deflected, viewed in the transverse direction of the vehicle, runs parallel to the longitudinal axis of the McPherson strut unit. As has been recognized, with this measure squeezing of the lower rubber-metal sleeve bearing can be prevented which otherwise occurs relative to the transverse arm as a result of a tilt of the McPherson strut unit which changes over the spring path of the wheel during deflection and rebound. This results in an improved response behavior in the spring system of the motor vehicle; stick-slip effects which may occur on the telescoping shock absorber are eliminated.

A design of the wheel suspension which is also advantageous with respect to the other driving properties of the motor vehicle consists in that the lower forward transverse arm is positioned essentially in the transverse direction of the motor vehicle and the rear lower transverse arm is positioned approx. 45° to the rear tilted inside thereto.

Furthermore, the body-side bearing points of the lower transverse arms can be aligned essentially horizontally at the same height, with which unwanted migration of the indicated lower bearing point of the McPherson strut unit over the entire spring path of the wheel suspension is likewise advantageously avoided.

In the conventional manner the tilt of the McPherson strut unit can be approx. 5 to 10 degrees up to the rear and up to the inside in order to effect easily manageable matching of the wheel-guiding transverse arms to the McPherson strut unit, in addition to a structurally favorable arrangement of the McPherson strut unit.

In this connection, the horizontal plane defined by the two lower transverse arms can also be aligned perpendicular to the tilt of the McPherson strut unit viewed in the transverse direction of the vehicle by a suitable design of the wheel carrier-side coupling points.

Finally, the body-side bearing of the forward lower transverse arm in the transverse direction of the motor vehicle can be made stiffer than in the direction of the longitudinal axis of the McPherson strut unit. This results in an additional improvement of driving comfort and the damping properties of the wheel suspension relative to the body of the vehicle without adversely affecting the guiding properties of the forward transverse arm.

One embodiment of the invention will be detailed below. The figures are schematic.

FIG. 1 shows, with one wheel carrier, two lower, detached transverse arms, a suggested track rod and a McPherson strut unit;

FIG. 2 shows a side view S of FIG. 1 of the wheel suspension; and

FIG. 3 shows a top view of the wheel arrangement as shown in FIGS. 1 and 2.

FIGS. 1 to 3 show the lower plane of the front left wheel suspension 10 for motor vehicles, which wheel suspension is composed essentially of two lower, individual transverse arms 12, 14, one wheel carrier 16, a track rod 18 which is only suggested, and a McPherson strut unit 20. The direction of travel of the motor vehicle is indicated by F. The wheel which is not shown is attached to the wheel flange 22 which is pivoted-mounted in the wheel carrier 16.

The transverse arms 12, 14 are separate transverse arms which are coupled to the body of the motor vehicle which is not shown (or an auxiliary frame) via angularly movable rubber-metal sleeve joints 12 a, 14 a and to the wheel carrier 16 via ball joints 12 b, 14 b (compare FIG. 2).

The third wheel guiding element, located in the lower plane of the wheel suspension 10, is the track rod 18 which is connected via a ball joint 18 a to a steering means of the motor vehicle which is not shown and also is coupled to one steering arm 16 a of the wheel carrier 16 via a ball joint 18 b.

In the wheel suspension 10 for non-steered wheels of a motor vehicle, the track rod 18 is coupled to the body as a further transverse arm.

The McPherson strut unit 20 is conventionally composed of a telescoping shock absorber 24 and a helical compression spring or support spring 26 which coaxially surrounds the shock absorber.

The piston rod 24 a of the shock absorber 24 is coupled via an absorber bearing which is not shown to a bearing bracket or directly to the body of the motor vehicle on which the upper end of the support spring 26 is also supported. The lower end of the support spring 26 is supported via a spring plate on the absorber cylinder 24 b of the shock absorber 24.

The absorber cylinder 24 b of the shock absorber 24 is furthermore coupled to the forward transverse arm 12 referred to as the support rod 12 below via a support part 24 c which is made slightly arc-shaped with a fork-shaped connecting part 24 d with interposition of a rubber-metal sleeve joint 12 c in the vicinity of the wheel carrier 16. The axis of the sleeve joint 12 c is aligned like the pertinent attachment screw 17 in the longitudinal direction of the motor vehicle.

On the neck 16 b of the wheel carrier 16 which is lengthened to the top, there are receiving holes for connecting the individual upper transverse arms (or a suspension arm) of the wheel suspension 10, for the sake of clarity, the individual transverse arms are not shown and neither are the disk brake means and the wheel of the wheel suspension 10.

The forward lower transverse arm or support rod 12 at this point is arranged such that the coupling point 12 c (center point of the sleeve joint 12 c) of the McPherson strut unit 20 on the support rod 12 when the wheel is deflected (spring path s) viewed in the transverse direction of the vehicle (compare FIG. 2) runs at least approximately parallel to the longitudinal axis (dot-dash line 28) of the McPherson strut unit 20. The longitudinal axis 28 of the McPherson strut unit 20 therefore changes only little over the deflection path of the wheel suspension 10 on 28 a and does not cause squeezing of the sleeve joint 12 c or unilaterally acting moments of the support spring 26 on the shock absorber 24.

For this purpose, the support rod 12, as is to be seen from FIG. 3, is positioned with a deviation of approx. 4 degrees (angle α), that is, more or less in the transverse direction of the motor vehicle (dot-dash line 30), and the rear lower transverse arm is positioned approx. 45 degrees (angle β) to the rear tilted inside thereto.

Furthermore the body-side bearing points 12 a, 14 a, and their rubber-metal sleeve joints 12 a, 14 a of the lower transverse arms 12, 14 are aligned essentially horizontally at about the same height.

The tilt of the McPherson strut unit 20 relative to the vertical is moreover 5 to 10 degrees up and to the rear and up to the inside, as is to be seen from FIGS. 2 and 3.

The two lower transverse arms are arranged skewed to one another. Their alignment is chosen such that parallel displacement of the lower rear transverse arm with the wheel-side articulation point 14 b into the articulation point 12 b of the support rod with the latter yields a plane which is almost perpendicular to the illustrated tilt (approx. 5 degrees) of the McPherson strut unit 20 viewed in the transverse direction of the vehicle 20.

Finally, the body-side bearing 12 a of the forward lower support rod 12 in the transverse direction 30 of the vehicle is designed to be stiffer than in the direction of the longitudinal axis 28 of the McPherson strut unit 20 (that is, in the vertical axis). These “spread” sleeve bearings are prior art and can have, for example, material-weakening lobes (in the vertical axis) or material-strengthening metal inserts (in the transverse axis), etc., and therefore are not shown. 

1-6. (canceled)
 7. A wheel suspension for a motor vehicle, comprising: a wheel carrier; a forward, lower arm pivotally connectable to said wheel carrier and pivotally connectable to a body of said vehicle, having a longitudinal centerline displaced from said wheel carrier at an angle of 4° relative to a transverse line of said vehicle, disposed perpendicular to the longitudinal axis of said vehicle; a rearward, lower arm pivotally connectable to said wheel carrier and pivotally connectable to said body, spaced 45° from said centerline of said forward, lower arm; an upper arm pivotally connectable to said wheel carrier and pivotally connectable to said body; and a McPherson strut connected to said forward, lower arm for pivotal displacement about a longitudinal axis relative to said vehicle, and connectable to said body, wherein said McPherson strut is disposed relative to said forward, lower arm so that when said suspension is mounted on said vehicle and said wheel carrier deflects, a center point of the pivotal connection of said McPherson strut and said forward, lower arm, would be caused to displace along a line of travel disposed substantially parallel to the longitudinal centerline of said McPherson strut.
 8. A wheel suspension according to claim 13 wherein said McPherson strut is tilted from the vertical in a transverse direction toward said vehicle in the range of 5° to 10° and is tilted from the vertical in a rearward direction in the range of 5° to 10°, when said suspension is mounted on said vehicle.
 9. A wheel suspension according to claim 13 wherein the pivotal connections of said lower arms are disposed horizontally when said suspension is mounted on said vehicle. 